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authorMarcin Nowakowski <marcin.nowakowski@imgtec.com>2016-09-30 11:33:46 +0200
committerRalf Baechle <ralf@linux-mips.org>2016-10-06 17:37:40 +0200
commitd05c513069f15be5de766026a4192998688ffff1 (patch)
tree7948594b560af72ed535a41cc567de4235562ff8 /arch/mips/kernel
parente3031b32840c1bee228c58bb284ebc05f97249c7 (diff)
downloadlinux-d05c513069f15be5de766026a4192998688ffff1.tar.bz2
MIPS: tracing: disable uprobe/kprobe on compact branch instructions
Current instruction decoder for uprobe/kprobe handler only handles branches with delay slots. For compact branches the behaviour is rather unpredictable - and depending on the encoding of a compact branch instruction may result in one (or more) of: - executing an instruction that follows a branch which wasn't in a delay slot and shouldn't have been executed - incorrectly emulating a branch leading to a jump to a wrong location - unexpected branching out of the single-stepped code and never reaching the breakpoint that should terminate the probe handler Results of these actions are generally unpredictable, but can end up with a probed application or kernel crash, so disable placing probes on compact branches until they are handled properly. Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/14336/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel')
-rw-r--r--arch/mips/kernel/branch.c34
-rw-r--r--arch/mips/kernel/kprobes.c6
-rw-r--r--arch/mips/kernel/probes-common.h2
-rw-r--r--arch/mips/kernel/uprobes.c6
4 files changed, 48 insertions, 0 deletions
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index f5c68483c98e..12c718181e5e 100644
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -866,3 +866,37 @@ unaligned:
force_sig(SIGBUS, current);
return -EFAULT;
}
+
+#if (defined CONFIG_KPROBES) || (defined CONFIG_UPROBES)
+
+int __insn_is_compact_branch(union mips_instruction insn)
+{
+ if (!cpu_has_mips_r6)
+ return 0;
+
+ switch (insn.i_format.opcode) {
+ case blezl_op:
+ case bgtzl_op:
+ case blez_op:
+ case bgtz_op:
+ /*
+ * blez[l] and bgtz[l] opcodes with non-zero rt
+ * are MIPS R6 compact branches
+ */
+ if (insn.i_format.rt)
+ return 1;
+ break;
+ case bc6_op:
+ case balc6_op:
+ case pop10_op:
+ case pop30_op:
+ case pop66_op:
+ case pop76_op:
+ return 1;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__insn_is_compact_branch);
+
+#endif /* CONFIG_KPROBES || CONFIG_UPROBES */
diff --git a/arch/mips/kernel/kprobes.c b/arch/mips/kernel/kprobes.c
index 747e3bf7bd9f..f5c8bce70db2 100644
--- a/arch/mips/kernel/kprobes.c
+++ b/arch/mips/kernel/kprobes.c
@@ -106,6 +106,12 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
goto out;
}
+ if (__insn_is_compact_branch(insn)) {
+ pr_notice("Kprobes for compact branches are not supported\n");
+ ret = -EINVAL;
+ goto out;
+ }
+
/* insn: must be on special executable page on mips. */
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn) {
diff --git a/arch/mips/kernel/probes-common.h b/arch/mips/kernel/probes-common.h
index c979c3790e4c..dd08e41134b6 100644
--- a/arch/mips/kernel/probes-common.h
+++ b/arch/mips/kernel/probes-common.h
@@ -13,6 +13,8 @@
#include <asm/inst.h>
+int __insn_is_compact_branch(union mips_instruction insn);
+
static inline int __insn_has_delay_slot(const union mips_instruction insn)
{
switch (insn.i_format.opcode) {
diff --git a/arch/mips/kernel/uprobes.c b/arch/mips/kernel/uprobes.c
index 1161c93a74cb..dbb917403131 100644
--- a/arch/mips/kernel/uprobes.c
+++ b/arch/mips/kernel/uprobes.c
@@ -36,6 +36,12 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *aup,
return -EINVAL;
inst.word = aup->insn[0];
+
+ if (__insn_is_compact_branch(inst)) {
+ pr_notice("Uprobes for compact branches are not supported\n");
+ return -EINVAL;
+ }
+
aup->ixol[0] = aup->insn[insn_has_delay_slot(inst)];
aup->ixol[1] = UPROBE_BRK_UPROBE_XOL; /* NOP */